That's what the workweek is for :-)
If you expect to get a working chunk of software from an employee for a fixed cost, that employee is essentially a contractor paid per working project. He definitely doesn't need his contract payment to support a needless manager who may very well be the cause of the bugs. Thus, he'll get that portion of what would go to the manager. And he doesn't need to pay for your billing department's building -- after all, that doesn't contribute anything to the success of his contract.
Load the employee at only 1.1x (the extra 10% to be used to pay for his office and some networking), and give him the additional 1.9x or so (effectively doubling or tripling his wages -- many employees are loaded at 2.0-3.0x), get rid of his managers, and give him a design document as accurate as a blueprint for building a wall, and the analogy might fit.
Basically, employee wages are "loaded" to account for this type of infrastructure, including having to do rewrites. Hopefully, hiring and management practices will work to minimize rewrites and bugs, and less time spent taking from the slush funds to do rewrites is more profit the company made.
TFA's analogy is like saying "why do we need network support? If it was installed correctly, it will never break."